1. Field of the Invention
The present invention relates to an image pickup apparatus such as a digital still camera and a digital video camera, and particularly to an image pickup apparatus having an auto zoom function capable of automatically keeping a constant size of an object in a captured image.
2. Description of the Related Art
Some image pickup apparatuses have a so-called auto zoom function (hereinafter simply referred to as “auto zoom”) that automatically performs zooming, when the image pickup apparatus is aimed at an object, so as to obtain image magnifications preset according to object distances. For example, Japanese Patent Laid-Open NO. 06-153047 discloses a camera that compares an area of a person's face detected in a captured image with a reference area and automatically performs zooming so as to always make the area of the face equal to the reference area.
Moreover, Japanese Patent Laid-Open NO. 2003-107335 discloses an image pickup apparatus that detects a person's face in a captured image, displays a focus detection area including the face and performs autofocus on the face in that focus detection area. This image pickup apparatus detects the person's face from the entire captured image, which can perform a good autofocus operation on the face regardless of a position and a region (size) of the person in the captured image.
However, in the camera disclosed in Japanese Patent Laid-Open NO. 06-153047, performing the auto zoom for the detected face without aiming direction change of the camera may cause disappearance of the face from the captured image. The possibility of such disappearance increases as a position of the face becomes farther from a center of the captured image (image pickup region). For example, FIG. 8A shows a case where an object 403 is located away from a center of a captured image 401. Reference numeral 402 denotes a face frame showing a region including a face of the object 403. In this case, performing zooming in a telephoto direction moves the object outward in the captured image 401 while increasing the size of the object 403 as shown in FIG. 8B.
Then, continuing the zooming in the telephoto direction finally moves the object 403 out of the image 401 as shown in FIG. 8C. This makes it difficult to recognize the object 403 from the captured image 401, and causes disappearance of the face frame 402.
It is possible to place the object at the center of the captured image by user's camera work. However, in particular, a fast zoom speed of the auto zoom often causes disappearance of the object within a short time.
Thus, the auto zoom causing such rapid disappearance of the object from the captured image causes the camera to repeat operation and stop of the zooming and to perform further zooming though the face has been already disappeared from the captured image.